Frequency selective amplifier having frequency responsive positive feedback



SEARCH "HUUIW.

3,193,779 ENCY July 6, 1965 c. A. BEATY FREQUENCY SELECTIVE AMPLIFIER HAVING FREQU RESPONSIVE POSITIVE FEEDBACK 3 Sheets-Sheet 1 Filed March 27, 1963 W m m r. T N mm m V m5 W c. A. BEATY 3,193,779 FREQUENCY SELECTIVE AMPLIFIER HAVING FREQUENCY July 6, 1965 RESPONSIVE POSITIVE FEEDBACK 3 Sheets-Sheet 2 n ON.

Filed March 27, 1963 WNW INVENTOR C/MEL 5 ,4 6m 7) July 6, 1965 c. A. BEAT/Y 3,193,779

FREQUENCY SELECTIVE AMPLIFIER HAVING FREQUENCY RESPONSIVE POSITIVE FEEDBACK Filed March 27, 1965 3 Sheets-Sheet 5 44\ 22 46 4a 2340 222a g 21 4 250 222 I96 2'54 244 158 2 24001 184 180 2 O k 206 174 v j INVENTOR. CbHRLES 4. 554 TV A TTOR/VKYS United States Patent O 3 193 779 FREQUENCY SELECTIVE AMPLIFIER HAVING ggggmrscv RESPONSIVE POSITIVE FEED- Charles A. Beaty, West Shore Blvd., Tampa, Fla. Filed Mar. 27, 1963, Ser. No. 271,041 17 Claims. or. 331-98) This invention relates to radio frequency devices having distributed parameter circuits. More specifically, the invention provides high performance and smaller size for radio frequency devices, including amplifiers and sources, employing transmission line construction.

Although many of the inventive features 'apply also to amplifiers, the invention is described embodied in microwave sources for producing continuous or frequency modulated output waves. The sources are advantageously used in communication equipment such as transmitters.

In general, such sources comprise an electronic valve, such as a vacuum tube, connected with a resonator in which electromagnetic waves can oscillate at radio frequencies. The electron beam of the vacuum tube delivers energy to the oscillating waves. A control circuit is coupled with the resonator and the tube to control the timing with which the electron beam delivers energy to the resonator. With the proper timing, the energy from the electron beam reinforces the oscillating waves in the resonator to achieve sustained oscillation. The oscillations are coupled from the resonator to furnish the output signal from the source. One description of transmission line sources and of suitable vacuum tubes is found in chapter of The Principles of Radar by Reintjes and Coate, published in 1952 by McGraw-Hill Book Company, Inc.

The present invention relates to the design and construction of an improved resonator and of a control circuit therefor. It also provides an improved support for the electronic valve. Other features of the invention relate to the manner in which the radio frequency energy is isolated from the DC. and other low frequency operating voltages.

The invention provides also a novel source of frequency modulated signals in which a variable reactance element is connected directly in a resonant circuit of the transmission line oscillator. With the preferred construction of this embodiment of the invention, the change in the resonant circuits reactance caused by the variable reactance element is multiplied, producing a large frequency deviation in the frequency modulated output signal.

In the prior art, microwave transmission line sources generally have a large axial length due to the bulky construction of the transmission lines that form the resonator and the control circuit. These transmission line sections are generally both constructed to resonate in an axial mode; that is, at resonance the voltage and current of the resonant standing wave in the transmission line vary along the axial length of the line. The choke circuits isolating the radio frequency energy from the DC. and other low frequency operating powers are similarly constructed with axially extending transmission line circuits that measurably increase the overall length of such sources.

The vacuum tubes in these sources are often supported in a cantilever fashion with a clamp at one end of the tube. Further, one or more coaxial transmission line cylinders or sleeves is held in place by spring fingers contacting a tube terminal, commonly for the grid element. Additional support for the grid sleeve is then undesirable because the support would have to pass through the space in one of the transmission line sections, introducing undesired impedance discontinuities. This con- 3,193,779 Patented July 6, 1965 struction is not rugged, and substantially limits the shock and vibration strength of the source.

With many prior constructions, bias connections, as required to deliver the grid potential that maintains the tube operating at the desired level, also pass through the space in a transmission line section. The presence of the bias conductor in the section provides a ready path for the radio frequencies to leak from the source, as well as presenting further impedance discontinuities in the section. The net effect of these multiple problems, encountered also with prior art amplifiers, is to substantially increase the cost and complexity of such radio frequency, and particularly microwave frequency devices.

It is an object of the present invention to provide improved radio frequency devices, including amplifiers and sources. Another object of the invention is to provide radio frequency devices that have small size. A further object of the invention is to provide devices of the above character that are rugged.

It is another object of the invention to provide radio frequency transmission line devices having simplified assembly, making possible manufacture at a low cost. Another object is to provide devices of the above character in which the parts are securely mounted and supported without having support structures that extend within transmission line sections.

It is also an object of the invention to provide continuous wave and frequency modulated sources of the above character for operation at microwave frequencies.

Yet another object of the invention is to provide radio frequency devices having simplified circuits for isolating the radio frequency energy from the low frequency operating voltages.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings, in which:

FIGURE 1 is a perspective view, partly broken away, of a continuous wave microwave source embodying the invention;

FIGURE 2 is a sectional side elevation view of the source of FIGURE 1 taken along line 2-2 of FIGURE 1;

FIGURE 3 is a sectional end elevation view of the source of FIGURE 1, taken along line 3-3 of FIGURE 2; and

FIGURE 4 is a sectional side elevation view of an embodiment of the invention for producing a frequency modulated signal.

GENERAL DESCRIPTION In general, as seen in FIGURE 1, a source 10 embodying the invention has a conductive cylindrical housing, indicated generally at 12, fitted with a coaxial output port 14 from which the desired radio frequency signal is coupled.

Terminals 16 and 18, recessed beyond the sources mounting flange 20, receive DC. and low frequency voltages for operating the source 10.

As shown in FIGURE 2, a high frequency triode indicated generally at 22, having a cathode terminal 24, a grid terminal 26, and an anode terminal 28, axially extends within the source housing 12 between the anode resonator or cavity 30, and a folded coaxial transmission line, often termed the cathode line, indicated generally at 32.

The anode cavity 30, with which the output port 14 is coupled to obtain the source output signal, extends radially about the triode 22 and operates in a radial mode. This makes it possible for the cavity 30 to have a short axial dimension and to be confined within the axial space between the anode and grid terminals 28 and 26 of triode 22. This compact design for the anode cavity 30 contributes to the small size of the present radio frequency devices and facilitates the realization of further advantageous features of the invention as described below.

An inner coaxial transmission line section 34 extends axially from the triode 22 and is in series with an outer section 36 to form the folded transmission line 32. This construction for the transmission line 32, with two overlapping axially extending sections, provides a marked reduction in the overall size of the radio frequency source, and makes possible additional advantages of the sources of the present invention.

A further feature of the radio frequency devices of the invention is the provision of a radial wall 38, seen in FIG- URE 2 between the cavity 30 and the remote end 32a of the outer section of the folded transmission line 32. The wall 38, forming a low radio frequency impedance at the folded lines remote end 32a, provides a firm support for a cylindrical grid sleeve 40 constituting part of the folded transmission line 32. The wall 38 also provides support for the triode 22, as well as forming a portion of the cavity 30. It will also be seen that the wall 38 is disposed between the cavity 30 and the folded transmission line 32 where it does not interfere with the space waves in these distributed parameter circuits.

It will now be apparent that with the present invention, radio frequency devices such as the source can be fabricated as a unitary casting forming the grid sleeve 40, the wall 38, and the larger portion of the housing 12. The present invention, by enabling construction of precision microwave devices through casting, greatly reduces their cost of manufacture. Radio frequency devices of this type constructed according to prior designs required a plurality of individually machined parts joined together as by silver soldering or brazing, all of which required the labor of highly skilled and highly paid technicians.

A source constructed as shown in FIGURES 1, 2, and 3 generates a continuous wave signal whose frequency can be tuned over a range of 50100 megacycles, as desired, about a central frequency in the vicinity of 2,000 megacycles. The oscillator of this invention is capable of producing output power of the order of 10 to watts.

FIGURE 4 shows another radio frequency device embodying the invention in a source of frequency modulated signals. The frequency modulated source indicated generally at 44 is generally similar to the source 10 of FIG- URES 1 through 3, with the addition of a varactor mount indicated generally at 46. The mount 46 is connected in the folded transmission line 48 to cause the oscillations in the anode cavity 50 to be frequency modulated according to the modulating signal applied to the modulating terminal 52 on the varactor mount 46.

The frequency modulated, or FM, source 44 can be constructed to deliver a signal in excess of 5 watts having a central frequency at around 2,000 megacycles electronically modulated to have a deviation of 10 megacycles.

CONTINUOUS WAVE SOURCE Housing Considering the source 10 in detail, with reference to FIGURE 1, a housing body portion 12a includes a cylindrical transmission line shell 54 joined at one end to the mounting flange 20. A larger diameter cylindrical cavity shell 56 is joined to the other end of the transmission line shell 54. This portion 12a of the housing can be cast as a unitary structure together with the radial flange wall 38 and the grid sleeve 40, shown in FIGURES 2 and 3, at a relatively low cost.

A housing end portion 12b is constructed with a conductive disc 58, seen at the right side of FIGURE 1, connected with the triodes cathode as described below. The disc 58 is assembled with the housing body portion 12a by screws 60 threadedly engaging an end flange 62, shown at the right of FIGURE 2 extending radially inward from the shell 54 of the housing body portion 12a. As also shown in FIGURE 2, an annular insulator 63 is sandwiched between the disc 58 and the end flange 62.

To present a low radio frequency impedance between the disc 58 and the inner edge 62a of the flange 62, the insulator 63 preferably extends between these elements for a radial distance of substantially a quarter-wavelength. Further, the insulator 63 is preferably thin. For operation at around 2,000 megacycles, the insulator can suitably extend between the disc 58 and flange 62 for 0.50 inch and have a thickness of 0.002 inch. The screws 60 are electrically insulated from the disc 58 to insulate the disc from the housing body portion 12a at low frequencies, by dielectric plugs 64. Further detail of a suitable construction for the plugs 64 is illustrated with the plug 66 shown at the right side of FIGURE 4.

As also shown in FIGURE 1, a resistor 68, commonly referred to as a grid leak resistor, is connected between the disc 58 of the housing end portion 12b and the shell 54 of the housing body portion 12a. The connection between the resistor 68 and the housing body portion 12a is made through the screws 70 that mount the resistor on the shell 54. The connection with the disc 58 is provided by passing the resistor lead 72 through the mounting flange 20 within an insulator 74. The lead 72 is then connected to the disc 58 by terminal 76.

Vacuum tube Turning now to FIGURE 2, the cathode terminal 24 of the triode 22, suitably tube type GL-6897 or its equivalent, is a conductive cylinder to which a first end of the tubes filament (not shown) is connected inside the tube. The other, second, end of the tubes filament is connected to a conducting cylinder coaxially disposed inside the cathode terminal 24 and insulated from it by a cylindrical insulator 82. With this construction for the triode 22, the low frequency filament voltage is applied between the cathode terminal 24 and the conducting sleeve 80.

The remainder of the external envelope for the triode 22, considered from right to left in FIGURE 2 starting from the cathode terminal 24, comprises in succession the cylindrical grid terminal 26, a cylindrical dielectric sleeve 86, and the cylindrical anode terminal 28. A plurality of radiators 78 extend beyond the housing end portion 12c for dissipating heat from the tubes anode.

Folded transmission line As shown in FIGURE 2, a hollow cylindrical cathode contacting sleeve 88, contacting the triode cathode terminal 24 at its inner end 88a, axially extends inward from the disc 58. The sleeves inner end 88a is suitably axially slotted to form a plurality of spring fingers contacting the terminal 24. Thus the filament and cathode voltages applied to the terminal 18 are conducted by the disc 58 to the sleeve 88 and applied to the cathode terminal 24.

A spring contact 90 axially extends from the filament terminal 16 through a hole 58a to contact the conducting cylinder 80 and connect with the second end of the filament of the triode 22. An apertured insulating plug 92 supports the terminal 16 and contact 90 insulated from the disc 58 and cathode contact sleeve 88. The plug 92 is preferably threadedly retained in the aperture 58a, as shown in FIGURE 2.

The grid sleeve 40 is formed as a hollow cylinder, as seen in the end view of FIGURE 3, formed with a pair of axially spaced apart internal shoulders 96a and 96b. A DC. and radio frequency grid contact 98, preferably formed as a ring-shaped helically-wound spiral of high conductive wire, is retained between the shoulders 96a and 96b radially compressed between the grid sleeve 40 and the triode grid terminal 26.

A ribbon of contact fingers 100 is formed into a cylinder and secured as by soldering to the inside of the grid sleeve 40 at its fixed anode end 40a to resiliently engage the triodes dielectric sleeve 86. The multiple contacts thus formed between the triode and the grid sleeve 40 firmly support the triode within the source housing and efficiently conduct heat, via the wall 38, from the grid and the cathode terminal regions of the triode to the housing 12.

It will now be seen that the folded coaxial transmission line 32 comprises an inner cylindrical conductor provided by the cathode contacting sleeve 88, and intermediate cylindrical conductor provided by the grid sleeve 40 and an outer cylindrical conductor provided by the transmission line shell 54 of the housing body portion 120. At the lines fold 32b, the cathode sleeve 88 and the shell 54 are coupled together by the radio frequency coupling between the disc 58 and the end flange 62. The lines remote end 32a is terminated with a low radio frequency impedance by the wall 38 connected between the shell 54 and the grid sleeve 40.

The overall length of the folded transmission line 32 is substantially three-quarters of a wavelength at the central operating frequency of the source 10. The length of the inner section 34 is somewhat shorter than a quarter wavelength to compensate for the internal grid to cathode capacity of the triode. The outer section 36 is accordingly made somewhat longer than a quarter wavelength. In the region of the fold 32b in the line 32, the free end of the grid sleeve 40 is spaced from the other conductors of the line 32 to maintain a fairly uniform impedance transition between the series-connected folded line sections 34 and 36. With this construction, the low impedance at the remote end 32a of the line is transformed to present the desired relatively high impedance at the input of the folded line, between the grid and cathode elements of the triode 22.

FIGURE 3 shows a threaded, capacitive tuning screw 102 protruding from the housing body shell 54 into the interconductor space in the folded lines outer section 36. The screw 102 is preferably axially positioned at the free end of the grid sleeve 40, where the intensity of the electric field in the line section 36 is relatively high. A support collar 104 is suitably mounted on the shell 54, as by silver soldering, and formed with an internal thread to support the tuning screw 102 and allow it to be threaded further into and out of the outer transmission line section 36 to adjust the frequency at which the folded transmission line 32 presents the desired impedance to the triode 22.

The conductive wall 38 radially extends between the grid sleeves fixed end 40a and the housing body portion 12a, as shown in FIGURE 2, and firmly supports the grid sleeve 40 to maintain it axially aligned within the source 10. The support provided by the wall 38 also holds the triode 22 firmly in position and conducts heat from its grid and cathode terminal regions.

Cavity As also shown in FIGURE 2, the wall 38 and the radial inner surface 56a of the cavity shell 56 form one radial wall of the cavity 30. The cavity shell 56 also forms the axial boundary of the cavity 30. An annular conductive disc 106, the housing end portion 12c, comprising a conductive anode clamp ring 108, together with the triode 22 complete the cavity 30.

The annular disc 106 is assembled to the cavity shell 56 with screws 110. The annular anode clamp ring 108 has a radial recess 108a in its inner surface to retain an anode contact 112 constructed with helically coiled wire as the grid contact 98. Screws 114, insulated from the clamp ring 106 by dielectric plugs 116 similar to the plugs 64 and 66 discussed above, clamp the anode ring 108 to the annular disc 106 with an annular insulator 113 between them. With this construction a relatively low radio frequency impedance is achieved between the ring 108 and the inner edge of the disc 106.

With the anode clamp ring 108 thus insulated from the annular disc 106 and the housing body portion 12a, which is at the same D.C. potential as the triodes grid terminal 26, the D.C. operating voltage for the triodes anode can be applied at terminal 118 on the clamp ring 108. Tube clamps 120 are also mounted on the ring 108 engaging the flanged end 28a of the anode terminal 28 to clamp the tube in the source 10.

As shown in FIGURES 1 and 3, a pair of tuning screws 122 and 124 radially extend from the cavity shell 56 into the cavity 30. The screws are threadedly retained in the cavity shell to adjust the central resonant frequency of the cavity 30, increasing the frequency as the length of the screw protruding into the cavity increases.

The output port 14, shown partly broken away in FIGURE 2, is suitably of the coaxial design having an outer conductor 126 coaxially disposed about an inner conductor 128. A conductive loop 130 is connected between the ports inner and outer conductors inside the cavity 30 to form a current probe. The outer conductor 126 of the probe 14 is suitably slidably retained by the cavity shell 56 to allow the probe to be rotated in the cavity to adjust the coupling between the conductive loop 130 and the cavity, thereby adjusting the amplitude of the signal coupled from the cavity to the port 14.

Considering the design and operation of the cavity 30, in the event that its axial length, between the annular disc 106 and the wall 38, was the same as the spacing in the triode between its anode and grid elements, the radial dimension of the cavity would suitably be a quarter wavelength. However, in the present source 10, the cavitys axial length is substantially larger, being selected on a largely mechanical basis considering, for example, the size of the output port 14, which the cavity accommodates. Hence the cavitys radial dimension is a foreshortened quarter wavelength so that the cavity is resonant in a radial mode at the central frequency of the range over which the device operates. In such a radial mode, the electric field in the cavity is predominantly in the axial direction with a maximum value at the center of the cavity and minimum intensity at the radial extremity. The axial length of the cavity 30 constructed to have a central resonant frequency in the neighborhood of 2,000 megacycles is 0.51 inch and the radial dimension is 1.275 inches.

Feedback Feedback between the cavity 30 and the folded transmission line 32 is provided with a pair of feedback conductors 132 and 134, shown in FIGURES 2 and 3, passing in apertures 136 and 138 through the wall 38. The feedback conductors 132 and 134 each form a loop in the cavity 30 as well as in the remote end 32a of the folded transmission line 32. One end of each feedback conductor is connected to the cavity wall and the other end to the inner surface of the transmission line shell 54, as shown in FIGURE 2. The amplitude of the feedback signal coupled from the cavity 30 to the transmission line 32 is determined by the area enclosed by the loops of the feedback conductors 132 and 134.

With this configuration, best shown in FIGURE 2, the conductors 132 and 134 deliver to the folded transmission lines 32 a feedback signal in phase with the energy in the cavity 30. The folded transmission line reverses the phase of this feedback signal to apply it between the grid and cathode elements of the triode 22 with the phase relationship required for the desired oscillator action.

Operation During the operation of the source 10 shown in FIG- URES 1, 2 and 3, a filament voltage is applied from a conventional external supply, not shown, between the terminals 16 and 18. A positive D.C. voltage, commonly referred to as the 13+ voltage, is applied to the triode anode terminal 28 by connection to the terminal 118 shown at the left side of FIGURE 2. The cathode D.C. terminal 18 is suitably connected to a negative D.C. voltage. The triode grid terminal 26 is then connected to ground through the housing body portion 12a; this connection is suitably provided by mounting the source with its mounting flange in contact with a grounded conductor. With these connections, it will be seen that the three housing portions, the body portion 12a, and the end portions 12b and 120 are at different voltages, being insulated from each other by the insulators 63 and 113 and plugs 64 and 116. The resultant operation of the source 10 as a continuous wave oscillator is commonly referred to as grounded grid operation.

With electromagnetic waves oscillating in the cavity 30 at the radio frequency to which it is tuned, which generally occurs spontaneously due to fluctuations in the DO voltages applied to the triode 22 and to noise voltages inherently generated by the triode, the feedback conductors 132 and 134 apply a portion of the oscillating energy to the folded transmission line 32. This feedback energy travels along the lines outer section 36 and onto the inner section 34, in series with it, to the triode 22.

With a preferred operation, the DC voltages applied to the triode 22 bias the grid sufiiciently negative to be nonconducting. The feedback signal applied between the grid and the cathode cause the grid potential to become more positive with respect to the potential at the cathode so that the triode conducts, and current is delivered from the cathode to the anode. In this manner, the triode amplifies at least a portion of the feedback signal applied to it, and in so doing delivers energy to the cavity 30 in phase with the oscillating cavity waves so that the cavity oscillations are reinforced. In this manner, sustained Oscillations are produced in the cavity 30. The conductive loop 130 of the output port 14 couples the oscillating energy from the cavity 30 for delivery to whatever external electrical load is connected to the port 14.

Adjusting the penetration of the tuning screw 102 in the folded line 32 and the screws 122 and 124 in the cavity 30 allows the frequency of oscillation to be controlled over a wide range.

It should be understood that with the present construction for the source 10, the feedback conductors 132 and 134 communicate between low impedance regions in the cavity 30 and in the folded line 32. Thus the feedback conductors are coupled between regions of high current or current faces. It will also be seen that with the present construction these regions of the cavity 30 and transmission line 32 that are highly suited for coupling by feedback loops are disposed adjacent each other for eflicient coupling with simple feedback conductors.

FREQUENCY MODULATED SOURCE Turning now to FIGURE 4, the source 44 of modulated radio frequency signals is designed and constructed in large part similar to the continuous wave source 10 of FIGURES 1, 2 and 3. Some differences between the sources 10 and 44, as may be seen from comparing the corresponding views of FIGURES 2 and 4, are directed to the frequency modulation operation of the source 44, while other changes stem from mechanical changes such as the manner in which the source is mounted, and the manner in which it is cooled. Accordingly, the FM source 44 utilizes a high frequency triode indicated at 142 having a cathode terminal 144, a grid terminal 146, an insulating cylinder portion 148, and an anode terminal 150. The cavity 50, resonant in a radial mode, is coupled between the anode and grid terminals 150 and 146, respectively, and the folded coaxial transmission line 48, comprising an inner section 152 in series with an outer section 154, is coupled between the triodes grid and cathode terminals. The folded transmission line 48 is coupled also with the cavity 50 by two feedback connections, one being indicated at 156, passing within apertures through wall 158, as indicated by the aperture 160.

A varactor 216, supported by mount 46, is also coupled with the folded transmission line 48 to vary the lines reactance according to the modulating signal applied to the modulating terminal 52. As discussed below, this causes a corresponding frequency modulation of the oscillating waves in the cavity 50. An output port 162 is coupled with the cavity 50 to deliver the frequency modulated signal to an external electrical load.

Housing The illustrated FM source 44 is constructed with a housing body portion indicated generally at 164, assembled with housing end portions indicated generally at 166 and 168.

A flanged conductive transmission line shell 170, having an internal end flange 172 for connection with the housing end portion 166, is bolted to a cavity shell 174 of a unitary member 176 to form the housing body portion 164. The unitary member 176 also includes the cylindrical grid sleeve 178 and the radial wall 158 joining the sleeve 178 with the cavity shell 174.

The shell is fitted with a conductive collar 173 that threadedly supports a tuning screw radially protruding into the outer section 154 of the folded line 48. The screw 155 is disposed adjacent the grid sleeve free end 1781) and provides a manual control over the operation of the folded line 48 similar to the tuning screw 102 of source 10, as shown in FIGURE 3.

The housing end portion 166, seen at the right side of FIGURE 4, includes a conductive disc 186 formed integrally with a cathode cont acting sleeve 188. A thi annular insulator 190 is disposed between the coplanar flange 172 and disc 186 for DC. insulation, and the screw 192 that clamps the disc 186 to the flange 172 is suitably insulated from the disc with the insulating plug 66. The filament voltage for the triode 142 is applied between terminals 194 and 196, and the DC. cathode connection is also made at the terminal 196 on the disc 186. A filament contact 198, suitably constructed like the contact 90 of the source 10, applies the filament voltage from the terminal 194 to the filament sleeve formed on the inner surface of the tubes cathode terminal 144. The filament contact 198 and the cathode contacting sleeve 188 preferably have a plurality of axial slots forming a plurality of circumferentially spaced spring fingers to enhance the contact between these elements and the respective contacts of the triode 142.

Folded transmission line The grid sleeve fixed end 178a has an internal annular recess for retaining a grid contact 182, suitably formed in the same manner as the contacts 98 and 112 described above with reference to FIGURE 2. The grid sleeve 178 extends axially from its fixed end 178a toward the housing end portion 166 to form the outer conductor of the folded tnansmission lines inner section 152 and the inner conductor of the folded lines outer section 154.

FIGURE 4 also shows a bevel 184 forming a transition between the grid sleeve 178 and the wall 158. As with the continuous wave source described above, the wall 158 is disposed intermediate the cavity 50 and the folded transmission line 48. The source 44 can be provided with a grid resistor (not shown) in the same manner that grid resistor 68 (FIGURES 1 and 2) is combined with the source 10.

The remote end 48a. of the folded transmission line 48 is thus terminated with a low radio frequency impedance by the wall 158 connected between the fixed end of the grid sleeve 178 and the transmission line shell 170. With the illustrated source 44 (FIGURE 4), the series coupled sections 154 and 152 of the line 48, preferably h V substantially uniform impedance throughout their lengths, have a combined electrical length of substantially three- 9 quarters of a wavelength at the operating frequency of the [FM source 44 to present a relatively large impedance between the grid and cathode elements of triode 142.

With this structure, the voltage standing wave in the transmission line 48 has a small value at the lines remote end 4811, and a relatively high value in the outer section 154 adjacent the free end 1781) of the grid sleeve. The lines voltage drops to a minimum value intermediate the ends of the inner section 152 and again rises to a high value where the inner section is coupled with the grid and cathode elements with the triode 142.

Cavity The cavity shell 174 of the housing body portion 164 can be formed with four radially extending holes equally spaced apart around the shells circumference; two such holes 200 and 202 are shown in FIGURE 4. The hole 200 is fitted with the output port 162, suitably constructed with a current probe 204 on a section of coaxial transmission line similar to the probe 14 discussed above with reference t-o FIGURE 2.

A cavity tuning screw 206 is threadably fitted in the hole 202. When additional holes are formed in the cavity shell 174 for threadably retaining tuning screws similar to the screw 206, the central frequency at which the FM source 44 operates can be varied over a wider frequency range than with a single tuning screw. Thus with three tuning screws, the central operating frequency can be varied over a range of approximately 100 megacycles centered at 2,150 megacycles.

Feedback The feedback connection 156 between the cavity 50 and the voltage transmission line 48 forms a conductive loop 156a in the cavity 50 and a similar loop 156]) in the remote end 48a of the line 48. The connection is suitably fabricated with a wire secured at one end, as by soldering, to a pin 157 radially protruding from the housing 'shell 170. The other end of the feedback wire is soldered in a hole in the housing shell 174 forming the cavity 50. The feedback between the cavity 50 and the folded transmission line 48 provided by the connection 156 and another connection, spaced 180 away (not shown), is similar to the feedback discussed above in the source 10.

The housing end portion 168 of the source 44 is suitably constructed with a conductive block 234 having successive cylindrical portions 234a, 234b and 234c of successively increasing diameter as shown at the left side of FIGURE 4. The block 234 is assembled with the housing body portion 164 by screws (not shown) passing through the cylindrical portion 234a and engaging the cavity shell 174. This construction may suitably be identical to the manner in which the anode clamp ring 108 shown in FIGURE 2 for the source is secured to the annular disc 106, and has insulating plugs between the mounting screws and the block 234. A disc-shaped insulator 236 is clamped between the block 234 and the cavity shell 174 for D.C. insulation. An annular dielectric band 238 may also be seated around the blocks cylindrical portion 234c adjacent the cavity shell 174 to prevent accidential short circuits between the housing end portion 168 and the housing body portion 164. The block 234 has an internal annular bore 240 having an enlarged anode seat 240a. An anode contact 242, retained in a recess 24011, is compressed between the triodes anode terminal 150 and the cylindrical portion 234c of the block.

The end cylindrical portion 234a is preferably formed with an axial slot 244 and fitted with screws 246 to clamp the triodes anode extension 248 in the cylindrical portion 234a.

Varactor mount Returning to the folded transmission line 48, a varactor mount 46, shown in FIGURE 4, is disposed in the folded line 48 to vary the reactance the line presents to the triode 142, and thereby serves to frequency modulate the output signal from the source 44 when a suitable modulat- 10 ing signal is applied to terminal 52, as described hereinafter.

The mount 46 is secured on the transmission line shell by a conductive collar 212 fitted with a set screw 214 that is tightened to clamp the mount with any desired degree of penetration in the outer section 154 of the folded line 48. The mount 46 comprises a varactor diode 216, having axially-spaced terminals 218 and 220, secured in the end of a conductive support 222.

The support 222 has a cylindrical body portion 222a that slidably fits within the collar 212. A cylindrical extension 2221) axially extends from the body of the support toward the grid sleeve 178.

An axial aperture 224, having an enlarged terminal seat 224a at one end and an enlarged varactor seat 224b at the other end, extends through the support 222. A terminal assembly 226, having a terminal 52 secured on a bored insulating body 228, is secured in the aperture seat 224a with the bore of the body 228 communicating with the aperture 224. With the insulating body 228 firmly secured in the seat 224a, the terminal 52 is insulated from the support 222 and from the remainder of the source 44 at D.C. as well as at radio frequencies.

An insulated conductive strand 230 is connected from the terminal 52 to extend through the bore in the in sulating body 228 and in the aperture 224 to a side hole 232 in the support. The strand 230 exits from the aperture 224 through the side hole 232 and connects to the bottom terminal 218 of the varactor 216.

The varactor is secured partly recessed in the support seat 224b as by bonding the varactor terminal 220 to the support with a conductive epoxy.

With this construction, the varactor terminal 218 is insulated from the remainder of the PM Source 44 and is connected by the strand 230, which is suitably left uninsulated after exiting from the side hole 232, to the terminal 52. The other varactor terminal 220 is connected to the housing body portion 164 of the source 44. Thus, a modulating signal applied between the housing body portion 164 and the terminal 52 is applied across the terminals of the varactor 216.

FM Operation Considering the operation of the varactor 216 in producing a frequency modulated output signal from the source 44, the modulating signal is applied between the terminal 52 and the housing body portion 164 to maintain the varactor back biased so that it functions as a variable capacitor rather than as a conventional diode. This operation is readily achieved with a modulating signal of uniform polarity and varying amplitude maintaining the anode terminal of the varactor 216 negative with respect to its cathode terminal.

A change in the amplitude of the modulating signal causes a corresponding change in the capacitance of the varactor between its opposite terminals 218 and 220. This change in the varactor capacitance is applied in parallel with the folded line section 154 and changes the reactance which the folded transmission line 48 presents to the triode 142 between its grid and cathode elements. As a result, the frequency at which oscillations are sustained in the cavity 50 varies according to the amplitude changes of the modulating signal applied to terminal 52.

FIGURE 4 shows the mount 46 axially disposed to support the varactor 216 in a radially extending position adjacent the remote end 1781: of the grid sleeve 178. Thus the varactor 216 is mounted in the outer section 154 of the folded transmission line 48 in a region of relatively intense electric field. It has been found that this design provides substantially superior frequency modulation performance, including a larger frequency deviation in the output signal, than is attained when the varactor is coupled in the anode cavity 50. It is thought that this improvement in operation is due, at least in part,

to amplification by the triode 142 of the change in reactance in the folded line 48, caused by the varactor 216. The amplified change in reactance thus produces in the cavity 50 a correspondingly increased change in the frequency of oscillation, and thereby produces the enhanced frequency modulation.

It will be seen that the construction of the mount 46 allows the position of the varactor support 222 to be adjusted within the collar 212 to change the spacing of the innermost varactor terminal 218 from the grid sleeve 178. As this spacing is increased, the power of the output frequency modulated signal coupled from the cavity 50 by the port 162 increases but the frequency deviation with which the output signal is modulated decreases. With a varactor-grid sleeve spacing to provide output signal power in excess of watts, the output frequency can be modulated to have a deviation as high as megacycles. The varactor diode used for this operation was a type MA 4336C, manufactured by Microwave Association, Inc. To avoid a short circuit between the innermost varactor terminal 218 and the grid sleeve 178, when the varactor is at its maximum penetration into the grid cavity 48, a thin sheet of high dielctric plastic insulation can be applied over the soldered connection at terminal 218.

As previously mentioned, in many prior art high frequency transmission line devices, a grid sleeve is supported within the device insulated from the devices outer shell or housing. In these prior art structures, the bias conductor for the grid element of the triode passes through the housing shell within an insulator so that no part of the housing shell is at the grid D.C. potential. With the device of the present invention, however, the grid sleeve 178 of FIGURE 4 is firmly supported in the device by the conductive wall 158. The housing pody portion 164 of the source 44 is then at the DC. grid potential and must be insulated from the housing end portions 166 and 168 which respectively are at the DC. potential of the triodes cathode and anode.

As described above, this insulation is achieved with the annular insulator 190 shown at the right side of FIG- URE 4 and with the annular insulator 236 shown at the left side. In addition, the screws that clamp the housing portions together include insulating plugs as described above.

Radio frequency energy is precluded from leaking out of the source 44 in the non-conducting gaps formed by these insulators 190 and 236 by providing a low radio frequency impedance, ideally a radio frequency short circuit, at the end of each gap inside the source. Accordingly, in the source 44, FIGURE 4, a low impedance is developed across the gap edge 172a in the folded line 48 and across the gap edge 250 in the cavity 50. The source 10 of FIGURES 1-3 is preferably similarly constructed.

The structure for achieving this desired D.C. insulation and radio frequency short circuit gap in the present sources is markedly smaller than the coaxial chokes commonly used in the prior art for these purposes.

With a preferred technique for providing a low radio frequency impedance, as across the gap edge 250 in the cavity 50 of the source 44, the radial length of the gap between the shell 174 and block portion 234a is made a quarter wavelength, or an odd multiple thereof, at the central radio frequency at which the source 44 operates. The spaced coplanar conducting surfaces 174a and 234d forming the gap then function as a quarter wavelength transmission line and transform the relatively high impedance at the outer end of the gap to the desired low impedance at the inner gap edge 250.

With an alternative construction, the gap width and gap length (radial) are selected so that the reactances associated with the conducting surfaces defining the gap are resonant at the desired radio frequency to present the low impedance.

In the source 44, the gap formed by insulator 236 is 0.003 inch wide and has a radial length of 0.51 inch. The gap formed by insulator is 0.003 inch thick and 0.50 inch long.

It should be noted that the use of the radially-extending insulator 190 between the housing body and end portions 164 and 166 of the source 44 is particularly advantageous with the folded transmission line design of the present devices. Contrary to prior art transmission line devices where the cathode line terminates at an axial extremity of the device corresponding to the right end of the source 44 of FIGURE 4, in the present devices the cathode line is folded to terminate at a point far removed from the right axial end of the source 44. As a result, a low radio frequency impedance is desired at the right end of the source 44 between the cathode sleeve 188 and the flange 172 of the housing body portion 170. In addition, this low impedance is not the only impedance reflected back to the triode 142, as found in many prior art constructions. On the contrary, with the source 44 the low impedance between the sleeve 188 and the flange 172 is in series with the impedance of the folded transmission line outer section 154. One advantage stemming from this structure is that frequency-dependent changes in the sleeve-flange impedance have a small effect on the total impedance presented to the triode by the folded line 48. It will be understood that these features, making possible small, high performance radio frequency devices, apply equally to the continuous wave source 10 in FIGURES 1, 2 and 3.

AMPLIFIER The structure of radio frequency devices according to the present invention can also be used for radio frequency amplifiers. To achieve operation as an amplifier with the construction shown for example in FIGURE 4, the varac tor mount 46 is replaced by a probe or similar element for delivering an input signal to the folded transmission line 48. In addition, the feedback connections between the cavity 50 and the folded line 48 are removed or otherwise altered to prevent oscillation. The triode 142 then amplifies the input signal applied to the folded line 48 to develop the desired output signal in the cavity 50.

The one-piece construction for the grid sleeve, the radial support wall and a portion of the housing, made possible with the present invention, is equall suited to amplifiers as well as the sources described above.

In summary, I have described a novel design for radio frequency and particularly microwave frequency devices having distributed parameter circuits such as cavities and transmission lines. The invention makes possible the construction of such devices with small size and low cost combined with high performance. It will be seen that the objects set forth above, among those made apparent in the preceding description are efiiciently attained with these devices and, since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific feat ures of the invention which, as a matter of language, might be said to fall therebetween.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A radio frequency device comprising in combination (A) an electronic valve having a first terminal, a second terminal, and a control terminal,

(1) the valve current between said first and second terminals being controllable by the relative potential of said control terminal with respect to said first and second terminals,

(B) a distributed parameter output circuit coupled be tween said first terminal and said control terminal,

(C) a control circuit coupled between said second terminal and said control terminal for controlling the energy delivered by said valve to said output circuit,

(1) said control circuit being constructed with a folded coaxial transmission line having first and second concentric and series-coupled coaxial sections,

(2) said second terminal being connected through relatively low radio frequency impedance to the outer conductor of said first coaxial section and to the inner conductor of said second coaxial section and said control terminal being connected through relatively low radio frequency impedance to the other conductors of said coaxial sections,

(D) a conductive housing for said valve, said output circuit and said control circuit,

(1) said housing forming aportion of said output circuit and a portion of said control circuit,

(E) a cylindrical sleeve within said housing and contacting said control terminal and constituting a part of said folded transmission line, and

(F) a conductive sleeve support connected between said sleeve and said housing intermediate said output circuit and said folded transmission line.

2. The radio frequency device defined in claim 1 in which (A) said output circuit is a cavity extending radially about said valve and operating in a radial mode,

- and (B) said support comprises a conductive annular wall radially extending outward from said valve to said housing.

3. Apparatus amplifying radio frequency signals comprising in combination,

(A) a conductive structure comprising (1) an outer hollow cylinder having first and second axial ends,

(2) an annular wall extending radially inward from said first end of said cylinder,

' (3) an intermediate cylindrical sleeve having third and fourth axial ends,

(a) said sleeve being connected adjacent said third end to the inner edge of said wall and coaxially extending within said cylinder to form therewith an outer coaxial transmission line section,

(B) a conductive inner cylindrical member having fifth and sixth axial ends and being coaxially disposed within said intermediate sleeve to form an inner coaxial transmission line section therewith,

(C) radio frequency coupling means coupling said transmission line inner section, at its end remote from said wall, in series with said transmission line outer section,

(D) an electronic valve having a first element, a second element, and a control element for controlling the valve current between said first and second elements,

(1) said second element and said control element being so coupled with said transmission line inner section, that a radio frequency potential between said inner cylindrical member and said intermediate sleeve is transferred to between said second element and said control element,

(E) input means for introducing a sign-a1 into said transmission line sections,

(F) a distributed parameter radio frequency output cuitcuit disposed on the other side of said annular wall from said transmission line inner and outer sections, and coupled between said first valve element and said control element and receiving energy from the valve current, and

(G) output means coupled with said output circuit for removing radio frequency signals from said output circuit.

4. Apparatus for amplifying radio frequency signals comprising in combination (A) a conductive structure comprising (1) an outer hollow cylinder having first and second axial ends,

(2) an annular wall extending radially inward from said first end of said cylinder,

(3) an intermediate cylindrical sleeve having third and fourth axial ends,

(a) said sleeve being connected adjacent said third end to the inner edge of said wall and coaxially extending within said cylinder to form therewith an outer coaxial transmission line section,

(B) a conductive inner cylindrical member having fifth and sixth axial ends and being coaxially disposed within said intermediate sleeve to form an inner coaxial transmission line section therewith,

(C) radio frequency coupling means coupling said transmission line inner section, at its end remote from said wall, in series with said transmission line outer section,

(D) a high-frequency vacuum tube having an anode,

a cathode, and a control grid,

(1) said cathode and said control grid being coupled, for radio frequency signal transfer, with said transmission line inner section,

(B) input means for introducing a signal into said transmission line sections,

(F) a radio frequency cavity formed in part by said annular wall and coupled with said tube anode to receive energy from the valve current, and

(G) output means coupled with said cavity.

5. The apparatus defined in claim 3 in which said radio frequency coupling means comprises (A) a conductive flange extending radially inward from said outer cylinder adjacent said second end thereof, and

(B) a conductive annular component extending radially outward from said inner member adjacent said sixth end thereof,

(1) said flange and said component being insulated from each other along closely spaced coplanar surfaces and (a) developing a relatively low radio frequency impedance between said coplanar surfaces at the inner edge of said flange.

6. The apparatus defined in claim 4 in which said input means comprise a feedback conductor passing through said annular wall and insulated therefrom between said output circuit and said outer transmission line section.

7. The apparatus defined in claim 3 further comprising (A) a variable reactance device having first and second terminals,

(1) the reactance of said device between said first and second terminals being controllable by a. voltage applied between them, and

(B) a mount supporting said variable reactance device coupled with said transmission line sections so that the impedance that said transmission line sections present to said valve varies according to the voltage applied between said first and second terminals of said device.

8. A radio frequency source comprising in combination (A) an electronic valve having a first terminal, a second terminal, and a control terminal for controlling the valve current between said first and second terminals,

(B) a resonant output cavity coupled with said first terminal and said control terminal to receive energy from the valve current,

(C) a conductive inner cylinder connected with said second valve terminal,

(D) a hollow conductive outer member having a cylindrical inner surface coaxial with said inner cylinder,

(E) a conductive intermediate cylindrical sleeve connected with said valve control terminal and coaxially disposed intermediate said inner cylinder and said inner surface of said outer member to form with said cylinder an inner coaxial transmission line section connected in series with an outer coaxial transmission line section formed with said outer member,

(F) a conductive annular wall connected between said sleeve and said outer member at the end of said outer transmission line section remote from the series connection with said inner transmission line section,

(1) said wall forming a portion of said output cavity,

(G) means forming a feedback signal path passing through said wall between said cavity and said outer transmission line section,

(1) said feedback path delivering to said outer transmission line section a feedback signal that is applied by said inner transmission line section to said valve to control the delivery of energy by said valve to said output cavity whereby radio frequency oscillations are sustained in said cavity.

9. The source defined in claim 8 further comprising (A) a first conductive annular flange extending from said inner cylinder at its end remote from said second valve terminal,

(B) a second conductive annular flange extending from said outer member substantially parallel to and closely spaced from a surface of said first flange to form a narrow gap communicating between said transmission line sections and an external surface of said source,

(1) said flanges being insulated from each other across said gap and being coupled together over a selected range of radio frequencies to develop a low impedance across the gap edge in said transmission line sections.

10. The source defined in claim 8 further comprising (A) a circuit element having two spaced terminals and whose radio frequency reactance is variable in response to a modulating voltage applied between said terminals, and

(B) a conductive mount supporting said element in said outer transmission line section oriented with its terminals spaced apart along the radius of said outer section,

(1) one of said element terminals being coupled with the inner conductor of said outer transmission line section and the other element terminal being connected with the outer conductor of the outer transmission line section,

(2) whereby the change in the reactance of said element produced by a modulating voltage applied between its terminals correspondingly changes the reactance which said transmission line inner section presents to said valve, to frequency modulate the oscillations in said output cavity.

11. A microwave source for operation with a vacuum tube having an anode terminal, a cathode terminal and a control grid terminal, said source comprising in combination (A) an anode contact for engaging said anode terminal,

(B) a housing for receiving said tube disposed along an axis, said housing (1) being mechanically connected with said anode contact,

(2) having a hollow conductive cavity element with a tubular inner surface disposed circumferentially around said axis and forming a portion of an anode cavity resonant in a radial mode,

(3) having a conductive member extending axially from said tubular surface of said cavity element and having a cylindrical inner surface,

(4) having a flange extending radially inward from said conductive member at the end of said cylindrical surface that is axially spaced from said tubular surface,

(C) a conductive cylindrical sleeve,

(1) having a fixed end and a free end,

(2) having a grid contact adjacent its fixed end for engaging said grid terminal,

(3) said sleeve being coaxial with said inner surface of said conductive member to form with said inner surface an outer section of coaxial transmission line,

(D) a conductive wall disposed intermediate said cavity and said transmission line and radially extending between said sleeve and said housing,

(E) a cathode cylinder (1) having contacts for engaging said cathode terminal,

(2) having a cylindrical outer surface disposed coaxially within said sleeve to form therewith an inner section of coaxial transmission line in series with said outer transmission line section,

(F) a conductive disc connected with said cathode cylinder at its end remote from said conductive wall and radially extending parallel to and closely spaced from said flange,

(1) said disc and said flange being coupled at the microwave frequencies of source operation to develop between them a low microwave impedance, and

(G) a feedback conductor passing between said cavity and said outer section of said transmission line through, and insulated from, said conductive wall,

(1) said feedback conductor being adapted to couple microwave energy from said cavity into said transmission line outer section for delivery via said inner transmission line section for application betwen said grid contact and said cathode contact.

12. The source defined in claim 11 further comprising (A) a varactor mount connected with and radially extending from said housing member into said outer section of transmission line,

(B) a varactor having first and second terminals on opposite ends thereof,

(1) said varactor being supported by said mount with said first and second terminals spaced between said inner surface of said housing member and said sleeve,

(2) said first terminal being connected with said mount,

(3) said second terminal being insulated from said mount and the remainder of said source (4) whereby a varying voltage applied across said varactor terminals produces a corresponding change in the reactance which said inner section of transmission line presents to said vacuum tube betwen its cathode and grid terminals, to frequency modulate the resonant microwave energy in said cavity.

13. A radio frequency device comprising in combination (A) an electron tube having, successively spaced along a first axis, an anode terminal, -a grid terminal and a cathode terminal,

(B) housing means including (1) an axially elongated conductive, tubular en closure having first and second ends and (2) means forming a vacuum tube mount mechanically connected to said enclosure and supporting said tube therein with said first axis substantially parallel to said enclosure axis,

(C) a first conductive member accessible at said first end of said enclosure and connected to said cathode terminal for applying direct current voltage thereto, said first conductive member being insulated from said enclosure,

(D) a second conductive member accessible at said second end of said enclosure and connected to said tube anode terminal for applying direct current voltage thereto, said second conductive member being insulated from said enclosure (1) the combination of said electron tube, said housing means, said first conductive member and said second conductive member forming a closed structure,

(E) means forming a distributed parameter output circuit within said housing means and coupled between said anode and grid terminals,

(F) means forming a distributed parameter control circuit within said housing means and coupled between said cathode and grid terminals,

(1) said distributed parameter circuits being axially spaced apart,

(2) one of said distributed parameter circuits being constructed as a folded coaxial transmission line,

(G) a conductor having a cylindrical outer surface disposed with its axis substantially parallel tosaid first axis and forming a portion of said folded transmission line, and

(H) a conductive, radially-extending wall disposed axially intermediate said distributed parameter circuits and connected between said grid terminal and said enclosure,

(1) said wall being connected to and supporting sa-id conduct-or from said enclosure.

14. The device defined in claim 13 (A) in which each of said distributed parameter circuits has a region of low radio frequency impedance adjacent said wall, and

(B) further comprising feedback means coupling between said distributed parameter circuits at said low impedance regions.

15. The radio frequency device defined in claim 13 in which the other of said distributed parameter circuits is a cavity concentric with said tube and resonant in a radial mode,

(A) each of said enclosure and said wall defining at least a portion of said cavity.

16. The radio frequency device defined in claim 15 in which (A) said first conductive member forms the innermost inner conductor of said folded transmission line, and

(B) said second conductive member defines a further portion of said cavity.

17. The radio frequency device defined in claim 13 further comprising a resistor disposed outside said enclosure and connected between said enclosure and said first conductive member.

References Cited by the Examiner UNITED STATES PATENTS 2,476,725 7/49 Gurewitsch 331-98 2,568,727 9/51 Freeman 331-98 2,681,997 6/54 Haefif et al. 331-98 2,689,915 9/54 Brown 331-98 2,752,495 6/56 Kroger 332-30 X 2,797,324 6/57 Midlock 331-98 2,867,726 1/59 Preist 331-98 2,895,076 7/59 Stocker 333-83 X 3,031,626 4/62 Dazey 331-97 X 3,039,064 6/62 Dain et al 331-177 X 3,045,146 7/62 Haegele et a1. 315-521 3,048,802 8/62 Jurcy 333-83 FOREIGN PATENTS 1,012,969 8/57 Germany.

ROY LAKE, Primary Examiner.

JOHN KOMINSKI, Examiner. 

1. A RADIO FREQUENCY DEVICE COMPRISING IN COMBINATION (A) AN ELECTRONIC VALVE HAVING A FIRST TERMINAL, A SECOND TERMINAL, AND A CONTROL TERMINAL, (1) THE VALVE CURRENT BETWEEN SAID FIRST AND SECOND TERMINALS BEING CONTROLLABLE BY THE RELATIVE POTENTIAL OF SAID CONTROL TERMINAL WITH RESPECT TO SAID FIRST AND SECOND TERMINALS, (B) A DISTRIBUTED PARAMETER OUTPUT CIRCUIT COUPLED BETWEEN SAID FIRST TERMINAL AND SAID CONTROL TERMINAL, (C) A CONTROL CIRCUIT COUPLED BETWEEN SAID SECOND TERMINAL AND SAID CONTROL TERMINAL FOR CONTROLLING THE ENERGY DELIVERED BY SAID VALVE TO SAID OUTPUT CIRCUIT, (1) SAID CONTROL CIRCUIT BEING CONSTRUCTED WITH A FOLDED COAXIAL TRANSMISSION LINE HAVING FIRST AND SECOND CONCENTRIC AND SERIES-COUPLED COAXIAL SECTIONS, (2) SAID SECOND TERMINAL BEING CONNECTED THROUGH RELATIVELY LOW RADIO FREQUENCY IMPEDANCE TO THE OUTER CONDUCTOR OF SAID FIRST COAXIAL SECTION AND TO THE INNER CONDUCTOR OF SAID SECOND COAXIAL SECTION AND SAID CONTROL TERMINAL BEING CONNECTED THROUGH RELATIVE LOW RADIO FREQUENCY IMPEDANCE TO THE OTHER CONDUCTORS OF SAID COAXIAL SECTIONS, (D) A CONDUCTIVE HOUSING FOR SAID VALVE, SAID OUTPUT CIRCUIT AND SAID CONTROL CIRCUIT, (1) SAID HOUSING FORMING A PORTION OF SAID OUTPUT CIRCUIT AND A PORTIN OF SAID CONTROL CIRCUIT, (E) A CYLINDRICAL SLEEVE WITHIN SAID HOUSING AND CONTACTING SAID CONTROL TERMINAL AND CONSTITUTING A PART OF SAID FOLDED TRANSMISSION LINE, AND (F) A CONDUCTIVE SLEEVE SUPPORT CONNECTED BETWEEN SAID SLEEVE AND SAID HOUSING INTERMEDIATE SAID OUTPUT CIRCUIT AND SAID FOLDED TRANSMISSION LINE. 